The company building Labor’s NBN has been asked to write a ''corporate plan'' based on the Coalition’s broadband policy.

Independent MP Rob Oakeshott, the head of the parliamentary committee set up to scrutinise Labor’s NBN rollout, has called on NBN Co to set its sights on the alternative policy.

Mr Oakeshott wants NBN Co to complete the plan quickly so that Australians can properly compare the two parties’ policies before the election.

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The committee met in Sydney on Friday to hear submissions from NBN Co executives about the rollout.

The cost of the NBN emerged as a key issue, with NBN Co chief executive Mike Quigley maintaining that Labor's figure of $37.4 billion to build the NBN was correct, and that he had new cost breakdowns of the rollout to support his estimates.

Opposition communications spokesman Malcolm Turnbull, also a member of the committee, has said that the NBN would cost as much as $94 billion to build.

Despite, NBN Co repeatedly announcing that the project has been progressing slower than expected over the past few years, Mr Quigley insisted on Friday that the NBN was progressing ''on time and on budget''.

He also told the committee that NBN Co should have been better informed about contractors' progress in rolling out the fibre for the NBN.

Earlier this year, NBN Co had to revise down the projected number of NBN connections by tens of thousands, after one contractor altered its own projections.

Mr Quigley said that in hindsight it was a fair assessment that NBN Co had not been sufficiently aware of how contractors were tracking.

''We should have been more involved in the details of the construction company,'' he said.

He maintained Labor's more expensive plan to run fibre optic cable to every house in Australia was a better solution than the Coalition's cheaper, slower alternative, which runs fibre to street corners and then piggybacks on copper for the ''last mile'' to the house.

Mr Quigley said there would be ''substantial'' costs to repair Australia’s ageing copper network if NBN Co was to switch to the Coalition’s version of the network.

''What we don't know is what is the state of copper in the network . . . There's substantial remediation to be done, we just don't know how much,'' he said.

Mr Quigley would not be drawn on whether using the existing copper would cut a third off the cost of the NBN, as the opposition says, but he said NBN Co could provide technical and business advice to policy makers on that.

Mr Turnbull included no estimate of these copper repair costs in his NBN policy document.

Mr Quigley talked the committee through 19 pages of pie charts with breakdowns of costs.

''I'm here to give the committee some confidence that $37.4 billion is the right number,'' he said.

However, Mr Quigley's estimated costs remained contentious. For example, on the amount it costs to connect a premises with fibre, Mr Quigley's forecast costs for future connections were about one-third of the price of what it had been costing to date.

Some on the committee, including supporters of Labor’s NBN such as Mr Oakeshott, Greens' Senator Scott Ludlum and Labor MP Michelle Rowland, listened intently to Mr Quigley. Mr Turnbull described some of Mr Quigley's assertions as ''misleading''.

Mr Turnbull pointed out that Labor’s preferred technique of connecting fibre to every apartment in an apartment block is complicated and costly, and asked whether NBN Co had considered the cheaper method of running fibre to the basements of apartment buildings.

The chief technology officer of NBN Co, Gary McLaren, admitted he had ''turned his mind'' to this idea.

Meanwhile, NBN Co confirmed on Friday that it would begin offering customers download speeds of up to one gigabit per second from December.

That would put Australia on a par with some of the fastest networks in the world and allow users to download movies or other large files very quickly.